This is a remix of the spool hubs I use. These fit more snug, and slide into the spool a bit further than the previous version. They're more beefy & stronger too. I can't find the file to the original version, but those would sometimes break when trying to remove them from the bed, so nevermind them. These do the job, while using less material than many other hubs.

There is no standard spool size, every manufacturer is different. Don't complain to me if they don't fit as-is. Measure your spool first, then scale in TinkerCad to your heart's content.